Blank for production of cathode starting sheets



D. R. MABEY July 1s, 1967 BLANK FOR PRODUCTION OF CATHODE' STARTINGSHEETS Filed Deo. 5; 1962 l l l l l l IN VEN TOR.

R. VMABEY DOUGLAS United States Patent O 3,331,763 BLANK FOR PRODUCTIONOF CATHODE STARTING SHEETS Douglas R. Malley, Salt Lake City, Utah,assignor to Kennecott Copper Corporation, New York, N.Y., a

corporation of New York Filed Dec. 3, 1962, Ser. No. 241,967 Claims.(Cl. 204-281) This invention relates to the electrolytic reiining ofmetals, especially copper, and constitutes an improvement on blankspresently employed for the electrolytic dep osition of cathode startingsheets.

In the production of metallic copper from its ores, slabs of the metalhaving a purity of about 991/2% are produced by pyrometallurgicalprocesses `for use as anodes in a linal stage of purication byelectrolysis. Copper ions from the anodes are deposited, free ofimpurities, on thin cathode starting sheets of pure copper, where theybuild up into thick slabs of pure copper.

The cathode starting sheets are usually manufactured in the reiinery byelectrolytic deposition of copper on polished and oiled blanks of copperor stainless steel. The deposited copper sheets are stripped on theblanks when they attain a thickness of about l@ of an inch. Stripping ismade possible because of -the polished and oiled surfaces on which thecopper is deposited. Nevertheless, stripping from conventional blanks isdifficult, because the copper deposits along the edges of the blank aswell as on the two mutually opposite broad faces thereof. The narrowedge strips along opposite lateral edges of the blank must be peeleddown and then the broad sheets must be loosened and strippeddownsimultaneously at both broad faces of the blank so as not to damage thelower margin of one or the other of the resulting two starting sheetsbecause of the bottom edge strip still joining the two sheets. Theresulting sheets must be trimmed and straightened.

Stripping of a formed starting sheet from a cathode blank is ordinarilyperformed manually lby use of a long handled, steel blade which isinserted between one of the formed sheets and the 'blank .and is thendrawn outwardly to slit the upper part of each narrow edge strip free ofthe adjoining formed sheet, whereupon the slitting is continuedldownwardly and the narrow edge strips peeled olf as waste. The bladetends to score the blank and thereby promote adhension of subsequentlyformed sheets. Also, the blank tends -to become pitted by electrolyticcorrosion along its upper margin immediately above the level of theelectrolyte in ythe electrolytic tank and to promote adhesion thereat.Moreover, because of the nature of the handling required by thiscustomary type of cathode blank, it is virtually impossible to applyautomation to this phase of a refinerys operation.

Principal objectives in the making of the present invention were to soconstruct a cathode blank as to facilitate the stripping of formedstarting sheets therefrom; to virtually eliminate starting sheetadhesion to the blank; to minimize, if not entirely eliminate, theformation of scrap or waste portions; to produce starting sheets of uniform and regular thickness and coniiguration, requiring only a minimumof trimming and straightening, if any; to enable automation techniquesto be easily developed for and applied to the stripping of cathodestarting sheets from cathode blanks; and to insure long and satisfactoryservice for the blank.

In accordance with the invention, the cathode blank comprises asubstantially rigid and coherent 'body of dielectric material,preferably a suitable plastic, adherently laminated for the most partbetween two at and smooth face s heets of copper, stainless steel, orother suitable and electrically conductive material, and otherwise pro-3,331,763 Patented July 18, 1967 viding a complete and continuousperipheral edging for such sheets in common, and margins therefor whichare flush therewith. ln this way, not only are the lateral and bottomedges land edge margins of the blank effectively protected against thedeposition of copper during the electrolytic formation of cathodestarting sheets on the broad faces of the blank, but the important upperedge margins of the blank are also protected from electrolyticcorrosion, pitting, and other deleterious eiects conducive to startingsheet adhesion. Each of the electrically conductive face sheets iscompletely surrounded by a peripheral margin of insulating material.Adherence of such face sheets to the dielectric body is essentiallycomplete throughout, so that the resulting laminate blank is unitary andimpervious.

Upward extensions of the electrically conductive face sheets, formedeither integrally therewith or as separate sheet members closely joinedthereto, are laminated Ihetween the upper marginal portions of thedielectric body at and extending upwardly from the face sheets, toprovide electrical leads which are connected at their upper ends to busbars.

It is presently preferred that these upward extensions of the facesheets be upwardly extending portions of the individual sheetsthemselves, brough-t in-to face-to-face juxtaposition between the uppermarginal portions of the dielectric body and silver-soldered orotherwise suitably bonded or joined in good electrically conductive,faceto-face relationship. It is important in this connection that theinward bends of such upwardly extending portions, where they leave theoutwardly-placed face sheets, be as abrupt as possible, so that thelower marginal areas of the respective upper marginal portions of thedielectric body can have protective thickness and still be Hush with theface sheets. Feather edges for such insulating arcas are undesirable,for there would be a tendency toward separation along such edges over aperiod of time, resulting in deposition of metal beneath such edges andadhesions of the formed starting sheets to the cathode blank. Moreover,there would be a tendency toward uneven deposition of metal along thedening edges of the face sheets, resulting in irregularity ofconfiguration for the electrolytically-formed starting sheets.

The same consideration applies to the lateral and lower boundaries ofthe face sheets, making it highly desirable that the joinders betweenface sheet edges and the insulatin'g margins provided by the dielectricbody be normal to the exposed, working faces of such sheets, or nearlyso.

The closest approach that l have found to the concepts involved in thisinvention is disclosed in U.S. Patent No. 1,468,838, issued Sept. 25,1923, to Charles H. Shuh, entitled Cathode for the Electrolytic Refiningof Metals, where two separate cathode plates or blanks are carried inpockets formed at respectively opposite faces of a supporting frame ofdielectric material. In order to retain these plates in the pockets andstill have their exposed faces ush with the insulating bottom andlateral side margins of the frame, confronting margins of plates andpockets are beveled. This means that the exposed faces of the -cathodeplates are underably bordered along their bottoms and lateral sides byfeather edges of the dielectric frame. Additionally, a separateextension of the supporting frame Iprovides more feather edges along thetop and leaves electrical lead extensions of such plates completelyexposed to the electrolyte.

There are shown in the accompanying drawing specic embodiments of theinvention representing what are presently regarded as the best modes ofcarrying out the generic concepts in actual practice. From the detaileddescription of thesepresently preferred forms of the invention, othermore specific objects and features will become apparent,

In the drawing: Y

FIG. 1 is a broadside elevation showing a preferred Vconstruction of'thecathode blank of the invention;

FG. 5, a similar section taken on the line 5 5 of FIG.V 1; and

FIG. 6, a sectionl corresponding to the upper portion of FIG. 4, butshowing a somewhat different construction.

Referring to the drawing:

The starting sheet cathode blank of FIGS. 1-5 isrshown as being of theusual rectangular configuration. It comprises a rigid andcoherent-sheet-like body of dielectric material laminated for the mostpart between two flat and smooth face sheets 11 and 12 of some suitableelectrically conductive material, such as copper or stainless steel, andotherwise providing a complete and continuous, peripheral, insulatingedging 13, 14, 15, and 16 for the two sheets in common, and sets ofmargins 13a, 14a, 15a, 16a and 13b, 14b, 15b, 16h for the respectivesheets, flush with their exposed faces.

The material of thel dielectric bodyshould 4be inherently impervious toelectrolyte or should be made soin some suitable manner, and the twosheets 11 and 12 are intimately bonded and are adherent theretothroughout, including their ed-ge faces, so that the resulting cat-bodeblank isV completely impervious to electrolyte when suspended in anelectrolytic cell.

Electrical leads in common for theseY face sheets 11V and 12 areprovided by respective upward extensions thereof 11a and 12a, which arepreferably intimately joined in close electrical relationship, as bysilver solder, and yare laminated between the dielectric material ofupper edging 16 as they extend therethrough, Their upper,

exposed portions are preferably cut away centrally to y provide anopening 17 for handling purposes, and their upper ends are fastenedbetween bus bars 19 and 2t), as by means of rivets 21. v

In order to avoid undesirable feather edges for the dielectricV materialof upper edging 16 where the upward extensions 11a and 12a of the facesheets bend inwardlypto form electrical leads, such bends should be asnearly at right angles as is practical, see the bends 22 and 23 in FIG.4. Likewise, to avoid uneven deposition of .metal and likelihood oflaniinae separation at the join- 'ders between face sheet edges and theinsulating margins 13a, 13b, 14a, 14b, etc., such joinders are madenormal to the exposed, working faces of such sheets, or as nearly so aspractical, see the joinders 24 and 25 in FIGS.

4`and 5. To avoid concentration of stress forces at the lower corners offace sheets 11k fand. 12, which would have a tendency to destroyadhesion at such corners if they were sharp, these corners arepreferably rounded, as at 26, FIG. l, and the confronting portions oft-he dielectric margins'are made correspondingly arcuate.

In `the embodiment of FIG. 6, la single sheet or plate of copperrorother electrically conductive material providesan electrical lead 30 forthe face sheets 31 and 32, such sheet or plate lead 30 extending belowand between the lupper portions of the face sheets 31 `and 32 andVjoined thereto in face-to-face, good electrical contacting relationshipin some suitable manner, as by means of silver solder.

Inthis embodiment, a single bus bar 33 is conveniently joined to theupper end of the single sheet or plate lead 3G as by means of welding34. Advantages of this embodiment over that previously described are theabsence of` any need to bend the face plates `and to solder themtogether, the fact that the joinders between the insulating uppermargins of the dielectric body `and the thereto, or injection or othermolding techniques, utiliz-Y ing suitable molds with appropriateprovisions for prepositioning of the face sheets, may be employed; Suchplastic materials as polyvinylchloride, polyurethanes, polyamides,unsaturated polyesters, vinyl acetate, various of the epoxy resins,various phenolic resins, etc. are satisfactory to a greater or lesskdegree depending upon particular fabrication techniques employed, `asare natural and synthetic rubbers, such |as butadiene-acrylonitrile andpolychloroprene. Various fillers, extenders, accelerators,l

catalysts, and exterior coatings can be lutilized, depending uponwhether fabrication is by cold or hot procedures and whether or not heatand pressure, for example by means of a laminating or vulcanizing press,are employed to achieve t-he close adherence of component laminaenecessary to produce required impermeability to the electrolyte utilizedin the electrolytic cell. All of this `will Ybe apparent to fabricatorsaccustomed to working with the indicated materials and techniques.

Various epoxy resins, such as that put out under Vthe proprietary nameEpon, bond particularly Well to electrolytic copperV and form anextremely strong dielectric body when -reinforced with woven or braidedglass fibers, which are available in several forms for convenient use.When this is done 4on a hand-fabricating basis, smoothing of the curedglass-reinforced epoxy resin by sanding and coating of the sandedsurfaces with a hard-setting liquid resin, such as an unsaturatedpolyester, to prevent wicking and thus render the reinforced materialimpervious, produce a Very satisfactory product. When done-by aninjection molding technique, the sanding and coating steps will normallybe unnecessary.

Because there are no edge joinders between face sheets vat oppositefaces of the blank nor likelihood of adhesion of electrolyticallydeposited starting sheets to the face sheets of the blank along the topmargins thereof,

or, infact, along any of the margins thereof, the cathode blanks of theinvention are especially well adapted to a vacuum stripping operation orto some other,V

handling technique that can be carried out and programmed on anautomatic basis.

Whereas there are here illustrated and described struc- Y Y K defining asubstantially unbroken area, said sheets,

being intimately bondedk to opposite broad faces of the dielectric body,Vinwardly Iof bounding margins thereof and substantially ush with andalso intimately bonded to said margins, so as to be bordered by saiddielectric material to form a laminated body; and electrical leadsintimately joined to the face sheets and extending internally of saiddielectric` body, through and emerging from a marginal edge portion andbetween'said opposite broad faces thereof; said' dielectric materialbeing set and bonded to'V the other components of the laminated bodyunder heat and pressure, whereby the face sheets are bordered by saiddielectric material, substantially ush therewith, and the entirelaminated body is essentially -unitary and impervious to electrolyte.

2. The blank of claim 1, wherein the electrically conductive face sheetsare completely bounded by the dielectric material, and the electricalleads are integral eX- tensions of the respective face sheets and arebent inwardly and brought together within the confines of t-hedielectric body, so as to be encased by `dielectric material within amargin of said dielectric body.

3. The blank of claim 2, wherein there are additionally provided a pairof bus bars extending transversely of the electrical leads exteriorly ofthe dielectric body -and receiving said leads therebetween; and whereinthere are also additionally provided means clamping said bus barstightly together about said leads, in good electrical conductiverelationship therewith 4. 'I'he blank of claim '3, wherein therespective electrical leads are sheets of electrically conductivematerial disposed in face-to-face contacting relationship las theyemerge from and extend beyondrthe dielectric body.

5. The blank of claim 1, wherein the electrical leads are provided by aseparate sheet of electrically conductive material extending between andintimately joined to the face sheets and projecting through a margin ofthe dielectric body.

6. The blank of claim 5, wherein there is additionally provided a busbar extending transversely of the electrical lead sheet exteriorly ofthe dielectric body, and wherein said lead sheet is secured to said busbar by welding.

7. The blank of claim 1, wherein the joinders of edge faces of therespective face s-heet with contiguous lp0rtions of the dielectric bodyare substantially normal to the broad faces of said sheets.

8. The blank of claim 1, wherein the face sheets are of rectangularconguration with corners thereof rounded. 9. The blank of claim l,wherein the dielectric body is a glass-iiber-reinforced plasticmaterial. 10. The blank of claim 9, wherein the plastic material 1s anepoxy resin.

References Cited UNITED STATES PATENTS 724,862 4/ 1903 Henry 204-281930,902 8/ 1909 'Thorp 2,04-281 1,018,901 2/1912 Haultain 204-2861,468,838 9/ 1923 Sc-huh 204-281 1,470,883 10/ 1923 Schuh 204-2812,332,592.J 10/ 1943 Norris 204-11 3,038,826 6/l962 Medl 161-1863,230,163 1/ 1966 Dreyfus 2.04-281 JOHN H. MACK, Primary Examiner.HOWARD S. WILLIAMS, Examiner.

R. MIHALEK, Assistant Examiner.

1. IN THE ART OF ELECTROLYTICALLY REFINING COPPER, A BLANK FOR THEELECTROLYTIC PRODUCTION OF CATHODE STARTING SHEETS, COMPRISING ASUBSTANTIALLY RIGID, SHEET-LIKE BODY OF POLYMERIC, RESINOUS, DIELECTRICMATERIAL; FACE SHEETS CONSISTING OF AN ELECTRICALLY CONDUCTIVE METALDEFINING A SUBSTANTIALLY UNBROKEN AREA, SAID SHEETS BEING INTIMATELYBONDED TO OPPOSITE BROAN FACES OF THE DIELECTRIC BODY, INWARDLY OFBOUNDING MARGINS THEREOF AND SUBSTANTIALLY FLUSH WITH AND ALSOINTIMATELY BONDED TO SAID MARGINS, SO AS TO BE BORDERED BY SAIDDIELECTRIC MATERIAL TO FORM A LAMINATED BODY; AND ELECTRICAL LEADSINTIMATELY JOINED TO THE FACE SHEETS AND EXTENDING INTERNALLY OF SAIDDIELECTRIC BODY, THROUGH AND EMERGING FROM A MARGINAL EDGE PROTION ANDBETWEEN SAID OPPOSITE BROAD FACES THEREOF; SAID DIELECTRIC MATERIALBEING SET AND BONDED TO THE OTHER COMPONENTS OF THE LAMINATED BODY UNDERHEAT AND PRESSURE, WHEREBY THE FACE SHEETS ARE BORDERED BY SAIDDIELECTRIC MATERIAL, SUBSTANTIALLY FLUSH THEREWITH, AND THE ENTIRELAMINATED BODY IS ESSENTIALLY UNITARY AND IMPERVIOUS TO ELECTROLYTE.